Fix closures.rs indent double-counting for wrapped params with return…

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+### Fixed
+- (Style Edition 2027) Properly format closures with wrapped parameters and an explicit return type instead of leaving the enclosing expression unformatted. Issue: [#7012](https://github.com/rust-lang/rustfmt/issues/7012).
+
 
 ## [1.10.0] 2026-07-21
 

src/closures.rs

@@ -351,7 +351,16 @@ fn rewrite_closure_fn_decl(
         prefix.push_str(&ret_str);
     }
     // 1 = space between `|...|` and body.
-    let extra_offset = last_line_width(&prefix) + 1;
+    let last_line = last_line_width(&prefix) + 1;
+    let extra_offset =
+        if prefix.contains('\n') && context.config.style_edition() >= StyleEdition::Edition2027 {
+            // The return type was pushed onto a line of its own, so `last_line_width` measures
+            // from column zero. Callers apply this offset on top of `shape`, so subtract the
+            // width already accounted for by `shape` to avoid counting the indent twice.
+            last_line.saturating_sub(shape.used_width())
+        } else {
+            last_line
+        };
 
     Ok((prefix, extra_offset))
 }

tests/source/issue_7012_style_edition_2024.rs

@@ -0,0 +1,27 @@
+// rustfmt-style_edition: 2024
+
+fn test() {
+    if outer {
+        if inner {
+            if even_more_inner {
+                let items = page
+                    .into_iter()
+                    .map(
+                        |list_media_response::ListEntry {
+                             cdn,
+                             media_id,
+                             length,
+                         }|
+                         -> Result<_, RequestError<BackupAuthCredentialRejected>> {
+                            Ok(ListMediaItem {
+                                cdn,
+                                media_id,
+                                object_length: length,
+                            })
+                        },
+                    )
+                      .try_collect()?;
+            }
+        }
+    }
+}

tests/source/issue_7012_style_edition_2027.rs

@@ -0,0 +1,27 @@
+// rustfmt-style_edition: 2027
+
+fn test() {
+    if outer {
+        if inner {
+            if even_more_inner {
+                let items = page
+                    .into_iter()
+                    .map(
+                        |list_media_response::ListEntry {
+                             cdn,
+                             media_id,
+                             length,
+                         }|
+                         -> Result<_, RequestError<BackupAuthCredentialRejected>> {
+                            Ok(ListMediaItem {
+                                cdn,
+                                media_id,
+                                object_length: length,
+                            })
+                        },
+                    )
+                      .try_collect()?;
+            }
+        }
+    }
+}

tests/target/issue_7012_style_edition_2024.rs

@@ -0,0 +1,27 @@
+// rustfmt-style_edition: 2024
+
+fn test() {
+    if outer {
+        if inner {
+            if even_more_inner {
+                let items = page
+                    .into_iter()
+                    .map(
+                        |list_media_response::ListEntry {
+                             cdn,
+                             media_id,
+                             length,
+                         }|
+                         -> Result<_, RequestError<BackupAuthCredentialRejected>> {
+                            Ok(ListMediaItem {
+                                cdn,
+                                media_id,
+                                object_length: length,
+                            })
+                        },
+                    )
+                      .try_collect()?;
+            }
+        }
+    }
+}

tests/target/issue_7012_style_edition_2027.rs

@@ -0,0 +1,27 @@
+// rustfmt-style_edition: 2027
+
+fn test() {
+    if outer {
+        if inner {
+            if even_more_inner {
+                let items = page
+                    .into_iter()
+                    .map(
+                        |list_media_response::ListEntry {
+                             cdn,
+                             media_id,
+                             length,
+                         }|
+                         -> Result<_, RequestError<BackupAuthCredentialRejected>> {
+                            Ok(ListMediaItem {
+                                cdn,
+                                media_id,
+                                object_length: length,
+                            })
+                        },
+                    )
+                    .try_collect()?;
+            }
+        }
+    }
+}